Recently, Integrated Circuits (ICs) mounted on a Printed Circuit Board (PCB) have been developed to operate with a high power consumption at a low operating voltage and a high operating frequency. Thus, the recently developed ICs consume a large amount of current.
An increase of consumed current in the ICs means an occurrence of voltage noise Vnoise caused by inductance of the PDN. The voltage noise Vnoise may be indicated by Equation (1) below.
                              V          noise                =                  L          ⁢                                    d              ⁢                                                          ⁢              I                                      d              ⁢                                                          ⁢              t                                                          Equation        ⁢                                  ⁢                  (          1          )                    
On the other hand, the voltage noise Vnoise occurring by Equation (1) causes a stable operation error in a corresponding IC, and also propagates through the PDN so as to have a bad effect on another IC adjacent thereto. Further, the voltage noise Vnoise radiates outside of a device and causes an Electromagnetic Interference (EMI) problem. Therefore, a design of the PDN capable of restraining the voltage noise Vnoise is very important.
In order to design the PDN considering the voltage noise Vnoise, it is essential to obtain information on IC current. The reason is because the IC current
      d    ⁢                  ⁢    I        d    ⁢                  ⁢    t  functions are a source of the voltage noise Vnoise.
Since a design of the PDN without a consideration of an accurate IC current causes significant use of an unnecessary de-coupling capacitor, a possibility of an over-design is significant. Further, an inaccurate value is deduced when a Power Integrity (PI) simulation, a Signal Integrity (SI) simulation, and an EMI simulation are performed in order to evaluate the performance of the system. Thus, there are many preceding researches and efforts for obtaining information on an accurate IC current, and currently researches have actively proceeded.
As an existing method of obtaining model information on the IC current, there are (1) a method of using information on Simulation Program with “http://en.wikipedia.org/wiki/SPICE, (2) a method of measuring current at a position of designing a bulk on a board and a de-coupling capacitor, and (3) a method of inserting a current probe in the IC.
(1) The method of using the SPICE model information of the IC is a method of obtaining the information on the IC current by using the SPICE model information of the IC. That is, if the SPICE model information of the IC is secured, the IC current information may be obtained by using a Chip Power Model (CPM) of a sentinel simulation tool. Accordingly, the IC current information may be extracted in a frequency range from a DC band to a several GHz band, and a system simulation in which all the IC, a package including the IC and a PCB including the IC and the package are considered, may be performed by using the IC current information. However, from a standpoint of a PCB designer, it is substantially difficult to obtain the SPICE information of the IC because of a problem such as an outflow of technology and the like. Although the designer obtains the IC current information with a help of an IC vendor, an IC current value may be obtained only under a very restricted environment. Accordingly, a value measured on the board may be substituted for the IC current value in order to obtain the IC current information in consideration of various operation circumstances and environments.
(2) The method of measuring the IC current at a position of designing the bulk and de-coupling capacitor is a method of obtaining the IC current by using a magnetic loop probe. That is, the current value measured at a position of the de-coupling capacitor and the bulk capacitor by using the magnetic loop probe is regarded as the IC current.
On the other hand, the IC current includes various current components, and each current component includes different frequency components. Accordingly, the IC current is established by a combination of the different frequency values.
FIG. 1 is a graph illustrating a frequency distribution of an IC current according to the related art.
Referring to FIG. 1, a capacitor supplying an IC with electric current depending on a frequency range is determined by each Self Resonance Frequency (SRF). That is, the IC current corresponding to a frequency range (iODC region) of more than several hundred MHz is an electric current (iODC) supplied by On-Die Capacitance (ODC) present in the IC, and the IC current corresponding to a frequency range (idecap region) of several MHz to several hundred MHz is an electric current (idecap) supplied by the de-coupling capacitor. Also, the IC current corresponding to a frequency range (ibulk region) corresponding to a frequency range equal to or less than several MHz is an electric current (ibulk) supplied by the bulk capacitor and a Voltage Regulation Module (VRM). Accordingly, the electric current measured on the de-coupling capacitor and the bulk capacitor corresponds to an electric current in a corresponding frequency range of the IC. However, there is a disadvantage in that the IC current component supplied by the ODC cannot be identified by this method. Further, if the PDN is constituted of a trace with a narrow width and the number of the de-coupling capacitor and the bulk capacitor is small, the measurement of the corresponding current is possible. However, in a situation in that the PDN is constituted of a plane and plural capacitors with the same capacitance are massed, the electric current must be simultaneously measured on the capacitors with the same capacitance by a plurality of current probes. Therefore, there is a disadvantage in that it is difficult to apply this method to this case.
On the other hand, (3) the method of inserting the current probe in the IC is a method of measuring the IC current by using the magnetic coupling scheme in which the current probe is inserted in the IC. If this method is used, the current component supplied by the ODC may be extracted. In comparison with the simplified current measurement model of the previous methods (1) and (2), this method has an advantage of providing very precise information. However, since the current probe is always inserted in the IC to be measured in order to use the method (3), there is a disadvantage in view of efficiency of a space and a cost.
Accordingly, a method of extracting an IC current, which is capable of obtaining IC current information in various operating circumstances and environments and extracting a component of the IC current supplied by On-Die Capacitance (ODC) is desired.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.